This invention relates to an automated apparatus and process for the controlled shutdown and start-up of a wastewater treatment system. The invention is particularly adapted for use with wastewater treatment systems that are not operated on a fulltime basis, but experience periods of inoperation.
U.S. Federal Regulations set strict limitations for water discharged into the environment from Publicly Owned Treatment Works (POTW). Such requirements, and others like them, dictate the management and regulation of the wastewater discharge to the POTW facilities. To meet these requirements, industrial users are being required to install wastewater pretreatment plants. These pretreatment plants will typically reduce the biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS) and other regulated parameters from the waste stream prior to discharge tot eh POTW. Though a significant investment of capital and day to day operational costs is typically less than the surcharges and fines levied by the treatment works, this is often not considered in the long term view.
The typical water treatment system is demanded upon 24 hours per day, 7 days per week (24×7). This presumption is that the system will be fed a constant flow of wastewater for treatment. The operation that is generating the waste is presumed to operate 24×7. The less typical operation is a plant that operated one or two shifts. Even three shifts, however will shut down over weekends or holidays. The treatment system will operate as long as there is demand, that is, influent wastewater.
For example, smaller operations may operate only 8-16 hours per day, 5 days per week. Whereas, a typical wastewater treatment system operates optimally on a continuous flow basis 24 hours per day. To enable the wastewater treatment system to operate continuously, even when wastewater is generated discontinuously, a buffer tank may be provided in advance of the treatment system. The tank buffers the feed to the treatment system by providing a reservoir during the down time of the production, thus ensuring a continuous wastewater flow between the day's shutdown and start-up the next day.
Of greater challenge is the shutdown of the wastewater treatment system during periods of no influent wastewater flow. Plants of this nature run 5 days per week, shutting down completely on Friday evening and restarting Monday morning, for example. The buffer tank would now have to be sized 5-7 times that required in the previous example. Though this solves the continuous flow problem, it the wastewater maintained in the buffer tank is biologically active and if it is left untreated as it would over the several days of the down time, the material in the tank can and will turn septic.
A solution offered would be to manually interrupt the flow to the waste treatment system, purge the system with clean water rinsing the system twice. Start-up after the shut-down is accomplished normally. This solution, however, requires a significant volume of fresh water to purge the system. Obtaining the needed fresh water represents a significant acquisition and discharge cost. It would be an improvement in the art to provide an apparatus and process for the shutdown and start-up of a wastewater treatment system that does no require an external source of fresh water. It would be a further advancement in the art to provide a self-contained apparatus and process for the shutdown and start-up of a part-time wastewater treatment system.